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80 results for “geographical isolation”
Data from: Geographical isolation and environmental heterogeneity contribute to the spatial genetic patterns of Quercus kerrii (Fagaceae)
Southwest China is one of the major global biodiversity hotspots. The Tanaka line, extending within southwestern China from its northwest to its southeast, is an important biogeographical boundary between the Sino-Japanese and Sino-Himalayan floristic regions. Understanding the evolutionary history of the regional keystone species would assist with both reconstructing historical vegetation dynamics and ongoing biodiversity management. In this research, we combined phylogeographic methodologies and species distribution models (SDMs) to investigate the spatial genetic patterns and distribution dynamics of Quercus kerrii, a dominant evergreen oak inhabiting southwest China lowland evergreen broadleaved forests (EBLFs). A total of 403 individuals were sampled from 44 populations throughout southwest China. SDMs and mismatch distribution analysis indicated that Q. kerrii has undergone northward expansion since the Last Glacial Maximum (LGM). Quantitative analysis revealed that the range expansion of Q. kerrii since the LGM exceeded that of the sympatric mid-elevation species Quercus schottkyana, likely owing to their contrasting distribution elevations and habitat availabilities. The historical climate change since the LGM and the latitude gradient of the region played an important role in shaping the genetic diversity of Q. kerrii. The genetic differentiation index and genetic distance surface of Q. kerrii populations east of the Tanaka line exceeded those to its west. The long-term geographic isolation and environmental heterogeneity between the two sides of the Tanaka line might increase species divergence patterns and local adaptation. This study provides new insights into the historical dynamics of subtropical EBLFs and the changing biota of southwest China.
Data from: Genomic signatures of geographic isolation and natural selection in coral reef fishes
The drivers of speciation remain among the most controversial topics in evolutionary biology. Initially, Darwin emphasized natural selection as a primary mechanism of speciation, but the architects of the modern synthesis largely abandoned that view in favour of divergence by geographic isolation. The balance between selection and isolation is still at the forefront of the evolutionary debate, especially for the world's tropical oceans where biodiversity is high, but isolating barriers are few. Here, we identify the drivers of speciation in Pacific reef fishes of the genus Acanthurus by comparative genome scans of two peripheral populations that split from a large Central-West Pacific lineage at roughly the same time. Mitochondrial sequences indicate that populations in the Hawaiian Archipelago and the Marquesas Islands became isolated approximately 0.5 Ma. The Hawaiian lineage is morphologically indistinguishable from the widespread Pacific form, but the Marquesan form is recognized as a distinct species that occupies an unusual tropical ecosystem characterized by upwelling, turbidity, temperature fluctuations, algal blooms and little coral cover. An analysis of 3737 SNPs reveals a strong signal of selection at the Marquesas, with 59 loci under disruptive selection including an opsin Rh2 locus. While both the Hawaiian and Marquesan populations indicate signals of drift, the former shows a weak signal of selection that is comparable with populations in the Central-West Pacific. This contrast between closely related lineages reveals one population diverging due primarily to geographic isolation and genetic drift, and the other achieving taxonomic species status under the influence of selection.
Data from: Evolution of life history traits in geographically isolated populations of Vaejovis scorpions (Scorpiones: Vaejovidae)
Geographical isolation can over time accumulate life-history variation which can eventually lead to speciation. We used five species of Vaejovis scorpions that have been isolated from one another since the Pleistocene glaciation to identify if biogeographical patterns have allowed for the accumulation of life-history variation among species. Gravid females were captured and brought back to the lab until giving birth. Once offspring had begun to disperse, measurements of female size, reproductive investment, offspring size, offspring number, and variation in offspring size were recorded. Differences in how each species allocated energy to these variables were analysed utilizing path analysis and structural equation modelling. Female and offspring size, litter size, and total litter mass differed among species, but relative energetic investment did not. Most significant differences among species were not present after removing the effect of female size, indicating that female size is a major source of life-history variation. Path analyses indicated that there was no size–number trade-off within any species and that each species allocates energy toward total litter mass differently. Additionally, as offspring size increased, the variation in offspring mass decreased. These results show that each species allocates the same relative amount of energy in different ways. The variation seen could be a response to environmental variability or uncertainty, a product of maternal effects, or caused by the sufficient accumulation of genetic differences due to geographical isolation.
Data from: Genome-wide differentiation in closely related populations: the roles of selection and geographic isolation
Population divergence in geographic isolation is due to a combination of factors. Natural and sexual selection may be important in shaping patterns of population differentiation, a pattern referred to as 'isolation by adaptation' (IBA). IBA can be complementary to the well-known pattern of 'isolation by distance' (IBD), in which the divergence of closely related populations (via any evolutionary process) is associated with geographic isolation. The barn swallow Hirundo rustica complex comprises six closely related subspecies, where divergent sexual selection is associated with phenotypic differentiation among allopatric populations. To investigate the relative contributions of selection and geographic distance to genome-wide differentiation, we compared genotypic and phenotypic variation from 350 barn swallows sampled across eight populations (28 pairwise comparisons) from four different subspecies. We report a draft whole-genome sequence for H. rustica, to which we aligned a set of 9493 single nucleotide polymorphisms (SNPs). Using statistical approaches to control for spatial autocorrelation of phenotypic variables and geographic distance, we find that divergence in traits related to migratory behaviour and sexual signalling, as well as geographic distance, together explain over 70% of genome-wide divergence among populations. Controlling for IBD, we find 42% of genomewide divergence is attributable to IBA through pairwise differences in traits related to migratory behaviour and sexual signalling alone. By (i) combining these results with prior studies of how selection shapes morphological differentiation and (ii) accounting for spatial autocorrelation, we infer that morphological adaptation plays a large role in shaping population-level differentiation in this group of closely related populations.
Data from: The tempo of trait divergence in geographic isolation: avian speciation across the Marañon valley of Peru
Geographic isolation is considered essential to most speciation events, but our understanding of what controls the pace and degree of phenotypic divergence among allopatric populations remains poor. Why do some taxa exhibit phenotypic differentiation across barriers to dispersal, whereas others do not? To test factors controlling phenotypic divergence in allopatry, we employed a comparative phylogeographic approach consisting of replicates of ecologically similar Andean bird species isolated across a major biogeographic barrier, the Marañon valley of Peru. Our study design leverages variation among co-distributed taxa in their degree of plumage, morphometric and vocal differentiation across the Marañon to examine the tempo of phenotypic evolution. We found that substantial plumage differences between populations required roughly two million years to evolve. In contrast, morphometric trait evolution showed greater idiosyncrasy and stasis. Our results demonstrate that despite a large degree of idiosyncrasy in the relationship between genetic and phenotypic divergence across taxa and environments, comparative studies within regions may reveal predictability in the pace of phenotypic divergence. Our results also suggest that social selection is important for driving differentiation of populations found in similar environments.
Data from: Phylogeography of a widespread lizard complex reflects patterns of both geographic and ecological isolation
A primary challenge for modern phylogeography is understanding how ecology and geography, both contemporary and historical, shape the spatial distribution and evolutionary histories of species. Phylogeographic patterns are the result of many factors, including geology, climate, habitat, colonization history, and lineage-specific constraints. Assessing the relative influences of these factors is difficult because few species, regions, and environments are sampled in enough detail to compare competing hypotheses rigorously and because a particular phylogeographic pattern can potentially result from different evolutionary scenarios. The silky anoles (Anolis sericeus complex) of Central America and Mexico are abundant and found in all types of lowland terrestrial habitat, offering an excellent opportunity to test the relative influences of the factors affecting diversification. Here, we performed a range-wide statistical phylogeographic analysis on restriction-site associated DNA (RAD) markers from silky anoles and compared the phylogeographic patterns we recovered to historical and contemporary environmental and topographic data. We constructed niche models to compare niche overlap between sister lineages and conducted coalescent simulations to characterize how the major lineages of silky anoles have diverged. Our results revealed that the mode of divergence for major lineage diversification events was geographic isolation, resulting in ecological divergence between lineages, followed by secondary contact. Moreover, comparisons of parapatric sister lineages suggest that ecological niche divergence contributed to isolation by environment in this system, reflecting the natural history differences among populations in divergent environments.
Figure 5 in Geographic isolation and human-assisted dispersal in land snails: a Mediterranean story of Helix borealis and its relatives (Gastropoda: Stylommatophora: Helicidae)
Figure 5. Results of biogeographic reconstruction using the DEC model in RASP using 1000 time-trees estimated with BEAST from the full dataset (see text). Maximum of three areas was allowed for ancestral ranges and unlikely disjunctive ranges were prohibited. The areas (A–F, in parentheses) of which the ranges of the terminals consist are shown in Figure 2.
Figure 2 in Geographic isolation and human-assisted dispersal in land snails: a Mediterranean story of Helix borealis and its relatives (Gastropoda: Stylommatophora: Helicidae)
Figure 2. Distribution of sampling sites and assignment of locally sampled individuals to major mitochondrial clades of the Mediterranean clade of Helix. Different symbols and colours correspond to different groups as in Figure 4. Areas used for biogeographic reconstructions are shown and labelled with letters corresponding to those in Figure 5. A, northern Adriatic basin; B, northern Africa; C, Apennine Peninsula and Corsica; D, Greece, western Aegean and Crete; E, eastern Aegean and western Anatolia; F, northern Levant.
Figure 1 in Geographic isolation and human-assisted dispersal in land snails: a Mediterranean story of Helix borealis and its relatives (Gastropoda: Stylommatophora: Helicidae)
Figure 1. Live individuals of the Mediterranean clade Helix species: H. cincta (A), H. borealis (B–E) and H. melanostoma (F). A, Cyprus, Kato Drys; B, Greece, Evvia, between Vassilika and Ellinika; C, Greece, Peloponnese, by Rogi near Kalavryta; D, Greece, Kefalonia: Asos; E, Greece, Peloponnese, near Sparti; F, north-western Tunisia, Kef Governorate, near Sers.
Figure 4 in Geographic isolation and human-assisted dispersal in land snails: a Mediterranean story of Helix borealis and its relatives (Gastropoda: Stylommatophora: Helicidae)
Figure 4. Detailed unrooted phylogeny of the Mediterranean clade inferred from a concatenated alignment of partial mitochondrial COI and 16S gene sequences. The tree is a 50% majority rule consensus of the posterior of a Bayesian analysis with MrBayes. Branch labels indicate SH-aLRT support values, standard bootstrap proportions from 1000 pseudoreplicates, and posterior probabilities from a Bayesian analysis, respectively. Only posterior probabilities are shown for some branches near the tips due to space constraints. Tips are labelled by isolate codes (our data) or GenBank accession numbers of 16S sequences (data from other authors) and two-letter ISO country codes; where needed for interpretation of the results, geographic origin of the sample is given, usually by the closest significant town. Red arrowheads point to samples presumed here to be taken outside of the native range of the respective species. Clade symbols and colours correspond to Figure 2. Abbreviations: anct, anctostoma; thiess, thiesseana; undesc, undescribed; valent, valentini.
Distribution. Horn of Africa (Eritrea, Djibouti, Ethiopia, and Somalia), geographically isolated from the other gundis. in Ctenodactylidae
Distribution. Horn of Africa (Eritrea, Djibouti, Ethiopia, and Somalia), geographically isolated from the other gundis.
FIGURE 3 in Geographically structured genetic variation in Ptychozoon lionotum (Squamata: Gekkonidae) and a new species from an isolated volcano in Myanmar
FIGURE 3. Deciduous dipterocap forest habitat of Ptychozoon popaense sp. nov. on Mt. Popa, Mandalay Region, Myanmar.
FIGURE 1 in Geographically structured genetic variation in Ptychozoon lionotum (Squamata: Gekkonidae) and a new species from an isolated volcano in Myanmar
FIGURE 1. Left: distribution of the samples of the Ptychozoon lionotum Group used in the molecular phylogenetic analysis. Right: Maximum likelihood consensus tree topology of Ptychozoon. Black dots denote nodes with BPP ¿ 0.95, UFB ¿ 95, and LRT ¿ 0.80. The grey dot denotes a node with BPP ¿ 0.95, UFB ± 95, and LRT ¿ 0.80. The open dot denotes a node with no significant support.
FIGURE 2 in Geographically structured genetic variation in Ptychozoon lionotum (Squamata: Gekkonidae) and a new species from an isolated volcano in Myanmar
FIGURE 2. Adult male holotype of Ptychozoon popaense sp. nov. (LSUHC 13508) from Yay Su camp, 16 km northeast of Kyauk-pa-taung Town, Kyauk-pa-taung Township, Mt. Popa, Mandalay Region, Myanmar.
Fig. 5 in Geographical versus ecological isolation of closely related black flies (Diptera: Simuliidae) inferred from phylogeny, geography, and ecology
Fig. 5 PCA of stream variables for three species in Clade II of subgenus Gomphostilbia in Thailand. Factor score 1 (PC-1) explained 39.01 % of the total variation and was related positively to stream width and related negatively to velocity and altitude. Factor score 2 (PC-2) explained 19.64 % of the total variation and was related positively to stream depth. Simulium chumpornense was distributed separately from other taxa of the clade along the PC-1 axis
Fig. 4 in Geographical versus ecological isolation of closely related black flies (Diptera: Simuliidae) inferred from phylogeny, geography, and ecology
Fig. 4 PCA of stream variables for two species in Clade I-3 of subgenus Gomphostilbia in Thailand. Factor score 1 (PC-1) explained 38.36 % of the total variation and was related positively to stream width, depth, velocity, and conductivity. Factor score 2 (PC-2) explained 29.41 % of the total variation and was related positively to water conductivity and pH. The two taxa of this clade were not separated in environmental space
Fig. 1 in Geographical versus ecological isolation of closely related black flies (Diptera: Simuliidae) inferred from phylogeny, geography, and ecology
Fig. 1 Maximum parsimony tree for Gomphostilbia in Thailand, based on combined dataset of the cytochrome oxidase I, cytochrome oxidase II, and 18 S rRNA/ITS1 sequences. Bootstrap values for
Fig. 3 in Geographical versus ecological isolation of closely related black flies (Diptera: Simuliidae) inferred from phylogeny, geography, and ecology
Fig. 3 PCA of stream variables for two species in Clade I-2 of subgenus Gomphostilbia in Thailand. Factor score 1 (PC-1) explained 49.49 % of the total variation and was positively related to water conductivity and pH. Factor score 2 (PC-2) explained 24.80 % of the total variation and was positively related to stream depth and negatively to altitude. The two taxa of this clade were not separated in environmental space
Isolation by geographical distance after release from Pleistocene refugia explains genetic and phenotypic variation in Xylotrupes siamensis (Coleoptera: Scarabaeidae)
<p class="BodyA">Consistent and objective species delimitation is crucial to biodiversity studies, but challenges remain when conflicting taxonomic decisions have been made because different data sets and analytical methods were used to delineate species. In the rhinoceros beetle, <em>Xylotrupes siamensis</em>, the use of different morphological characters has resulted in taxonomic disagreement between studies. We used three molecular loci (mitochondrial <em>CO1</em> and nuclear ITS2 and <em>H3</em>) to investigate the genetic divergence between populations exhibiting different male horn phenotypes. We also applied an approximate Bayesian computation approach to test alternative historical hypotheses that might explain the present genetic diversity among geographical populations. Furthermore, we used species distribution models to estimate the temporal variation in the geographical distribution of suitable habitats. The results show that the two phenotypic taxa within <em>X. siamensis</em> are not genetically structured and that their genetic structure can be explained using isolation by geographical distance. The emergence of the two phenotypic taxa might have been associated with historical isolation in separate refugia. However, spatial expansion and genetic interchange between populations might have gradually eroded the spatial genetic structure. We demonstrate that understanding the historical processes responsible for phenotypic divergence and genetic diversity among current populations could help with making evolutionarily coherent taxonomic decisions.</p>
Figure 3 in Isolation by geographical distance after release from Pleistocene refugia explains genetic and phenotypic variation in Xylotrupes siamensis (Coleoptera: Scarabaeidae)
Figure 3. Phylogenetic networks of the three analysed loci and three historical scenarios explaining the origin of the CLAOS population tested using the DIYABC program. The colour of each individual shown in the network corresponds to the taxonomic assignment colour in the DIYABC analysis. Scenario 2 was the most likely model selected by the program (~60% posterior support), and scenario 1 also received moderate support (~30% posterior support). Results of posterior support among scenarios and model checking, in addition to the estimated parameter values (population sizes and divergence times), can be found in the Supporting Information (Figs S3–S8).
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